The purposes of the study are to evaluate the effect of 40 mg of prevastatin administered once daily in dyslipidemic (LDH cholesterol concentration >130mg/dl, triglyceride concentration > 90th percentile for age and HDL cholesterol concentration < 35mg/dl despite dietary intervention) patients with respect to plasma total cholesterol, LDL cholesterol, VLDL cholesterol, HDL cholesterol, and triglycerides. It is a randomized, double blind, placebo-controlled, cross-over trial with a 6 week dietary lead in period, followed by two week 6-week blinded active treatment periods of prevastatin 40mg or matching placebo separated by a 6-week washout period.